Rocket propulsion method



July 28, 1959 A. ZLETZ ETAL 2,896,402

ROCKET PROPULSION METHOD Filed Feb. 16, 1953 OR I 4- /3 /C /6 OX/D/ZER Alex Z/efz y Dan 1?. Oarmody IN V EN TORS 2,896,402 ROCKET PROPULSION METHOD Alex Zletz, Park Forest, and Don R. Carmody, Crete, Ill., assignors to Standard Oil Company, Chicago, 111., a" corporation of Indiana Application February 16, 1953, Serial No. 336,905

15 Claims. (Cl. 6035.4)

This invention relates to the generation of gas. More particularly, it relates to reaction propulsion by the hypergolic reaction of a liquid fuel and a liquid oxidizer. Still more particularly, the invention relates to a method of rocket propulsion by the hypergolic reaction of a fuel and a hydrogen peroxide oxidizer, which material's spontaneously react to generate gas at high pressure and high temperature.

Reaction propulsion is now being used for many aerial purposes. For many usesit is necessary to operate. with a fuel system which is not dependent on atmospheric oxygen. This fuel system may consist of a single self-contained propellant or it may consist of aseparate fuel and a separate oxidizer, i.e., a bipropellant system.

In the bipropellant system the fuel and the oxidizer are introduced separately and essentially simultaneously into the combustion chamber of the reaction motor. The products of oxidation from the reaction of the fuel and the oxidizer are discharged through an orifice at the exit end of the combustion chamber and thereby produce the driving force. Because of the possibilities of electrical and/ or mechanical failure of the auxiilary methods of ignition such as a spark or a hot surface, it is preferred to use a self-igniting fuel system. A fuel which is self-igniting, i.e., spontaneously combustible when contacted with an oxidizer, is known as a hypergolic fuel.

Temperature has an important effect on the hypergol'ic activity of fuels. The temperature at the earths surface may vary from a high of about +125 F. to a low of as much as 65 F.; in general temperatures below about 20 or 30 F. are exceptional. Thus surface-to-air missiles or rocket-driven aircraft should be capable of operation when the temperature of the fuel and the oxidizer at the moment of initial contact in the combustion chamber of the rocket motor is on the order of -20 F. Temperatures at high altitudes are frequently on the order of 65 F. and are known to approach -100 F. Thus an air-to-air missile should be able to operate satisfactorily when the temperature of the fuel and the oxidizer at the moment of initial contacting in the combustion chamber is on the order of 65 F.

The more common oxidizers are White fuming, nitric acid, red fuming nitric acid and nitric acid-sulfuric acid mixtures. While these nitric acid oxidizers operate satisfactorily over a wide range of atmospheric temperatures they have important drawbacks. The nitric acid oxidizers are extremely corrosive; they have poor storage stability; they give off toxic gases; and special precautions must be taken by personnel who handle these oxidizers.

Concentrated aqueous hydrogen peroxide solutions have excellent storage stability and do not give off harmful gas. However, these aqueous hydrogen peroxide solutions such as 90% hydrogen peroxide have the disadvantage of comparatively high freezing points, e.g., 90% hydrogen peroxide solution freezes at +12 F. The freezing point of 80% hydrogen peroxide is 9 F., but the activity of this solution toward the prior art fuels is markedly lower than the 90% H 2,896,402 Patented July. 28, 1959 solution. The freezing point of aqueous hydrogen peroxide solutions can be depressed. :by dissolving therein inorganic salts, preferably ammonium nitrate. Thus a solution containing 40 weight percent of ammonium nitrate and in which the hydrogen peroxide-water portion contains 90 weight percent of H 0 has a freezing point of about 30 F; A so-called H O2-30% NH NO3 solution has .a freezing point of. below 70 F.

Concentrated aqueous hydrogen peroxide solutions have been used as monopropellants by catalytically decomposing the hydrogen. peroxide, using such catalysts as potassium permanganate or copper oxide. Since the decomposition products contain free-oxygen the monopropellant' system is ineflicient. However, fuels which are hypergolic with nitric acid oxidizers maybe much less active or even inactive with concentrated H 0 solutions. Anhydrous hydrazine is usually considered to be the only fuel that is sufliciently hypergolic with concentrated H 0 solutions to be" practical; however, hydrazine' has the disability of a comparatively high freezing point. Some fuels are operative with H 0 solutions in the presence of a H 0 decomposition catalyst. Furthermore, the prior art fuels are less effective with ammonium nitrate containing H 0 than with H 0 alone.

An object of this invention is a method of generating gas by the hypergolic reaction of a mixed fuel and a hydrogen peroxide oxidizer. Another object is a method of reaction propulsion by the hypergolic interaction of a mixed fuel and a hydrogen peroxide oxidizer. Still another object is a method of reaction propulsion by the hypergolic interaction of a: hydrogen peroxide oxidizer and a mixed fuel which contains appreciable amounts of miscible hydrocarbons, particularly non-hypergolic liquid hydrocarbons. A particular object is a method of generating gas by the hypergolic interaction of a defined mixed fuel and; an oxidizer consisting of an aqueous hydrogen peroxide solution containing dissolved ammonium nitrate. Another particular object is a method of. rocket propulsion by the hypergo'lic interaction of a defined halide promoter containing mixed fuel and a defined hydro gen peroxide oxidizer at lower atmosphere temperatures. Other objects will become apparent in the course of the detailed description of the invention;

A method has been discovered for generating gas, which gas may be used as a substitute for compressed air for certain purposes or for driving the turbine of a jet engine or for rocket propulsion, which method comprises contacting- I An oxidizer selected from the class consisting of.

(i) Aqueous hydrogen peroxide solutions .w-liich contain at least about 80 weight percent of H 0 and the remainder is essentially water, and

(ii) Aqueous hydrogen peroxide-inorganic salt solutions wherein the hydrogen peroxide-water portion contains at least about 80 weight percent of H 0 II. A mixed fuel consisting essentially of at least an effective amount of (i) An inorganic halide promoter M X wherein M is selected from the class consisting ofphosphorus, boron, titanium, silicon and sulfur and X is selected from the class consisting of chlorine and bromine, and

(ii) A non-halogenated liquid organic fuel that is characterized by reactivity with said' oxidizers.

The oxidizers of this invention may be either concern trated aqueous hydrogen peroxide solutions or aqueous hydrogen peroxide solutions containing dissolved inor- .ous hydrogen peroxide solutions.

ganic salts, for example, ammonium halides, sodium sulfate, sodium nitrate, etc. Because of its marked favorable effect on reactivity, it is preferred to use ammonium nitrate containing solutions. The concentrated aqueous hydrogen peroxide solutions should contain at least about 80 weight percent of H the remainder of the solution is essentially water.

The hypergolic activity of the aqueous hydrogen peroxide solution is improved by increasing the concentration of the peroxide. Commercially available 90% H 0 solution is an excellent oxidizer above its freezing point. For operation at temperatures below about 0 F. aqueous H O -ammonium nitrate solutions, such as, 90%-40% or 80%-30% solutions are preferred.

Concentrated aqueous hydrogen peroxide solution as made commercially is virtually only H 0 and water. In order to improve storage stability small amounts of stabilizers may be added to the solution, e.g., sodium stannate, tetrasodium pyrophosphate, adipic acid, tartaric acid; in general only trace amounts of stabilizers are added so that the solution consists essentially of hydrogen peroxide and water.

In order to depress the freezing point of aqueous hydrogen peroxide solutions soluble inorganic salts are dissolved therein, e.g., sodium nitrate, ammonium chloride and ammonium nitrate have been used. These salt-containing solutions are commonly designated in terms of the weight percent of salt in the total solution and the weight percent of hydrogen peroxide present in the aqueous portion of the solution, e.g., 90% H O 40% NH NO indicates that the total aqueous hydrogen peroxide-nitrate solution consists of 40 weight percent of ammonium nitrate and 60 weight percent of aqueous hydrogen peroxide composed of 90 weight percent of H 0 and the remainder essentially water. This particular solution has a freezing point of about 30 F. A temperature of -70 F. is attainable with an 80% H O --3O% NH NO solution. It is preferred to operate in the presence of ammonium nitrate because of the pronounced favorable effect on the hypergolic activity of the fuels of this invention.

Certain inorganic halides promote the rate of reaction of certain non-halogenated liquid organic fuels with aque- The improvement in reactivity is especially pronounced with hydrogen peroxide-ammonium nitrate solutions. The inorganic halide promoters have the empirical formula M X where n and y are integers having values of 1 or higher. The symbol X represents a member of the class consisting of chlorine and bromine. The symbol M represents a member of the class consisting of phosphorus, boron, titanium, silicon and sulfur. Some examples of the halide promoters of this invention are phosphorus trichloride, phosphorus tribromide, boron chloride, titanium tetrachloride, silicon tetrachloride, sulfur monochloride and sulfur dichloride.

The halide promoters should be miscible with the fuel to attain maximum improvement in reactivity. The liquid halide promoters which have a relatively low freezing point, such as the phosphorus trihalides, are preferred.

Certain liquid organic compounds or mixtures thereof react with hydrogen peroxide to form oxidation products such as CO H O, S0 etc. The rate of reaction (reactivity) of organic compounds with hydrogen peroxide varies between generic classes and also among the species in a generic class. Some compounds are sufliciently inert to hydrogen peroxide at atmospheric temperatures that they are not benefited by the presence of reasonable amounts of halide promoter; and may actually impair the reactivity of the halide promoter with hydrogen peroxide, i.e., these inert materials are diluents.

For the purposes of this description, a reactive organic fuel is one that reacts with aqueous hydrogen peroxide oxidizers containing 80 weight percent of H 0 when contacted at temperatures between about 60 and F. with the oxidizer in a volume ratio of about 0.5:1 or less of fuel to oxidizer. The reaction is evidenced by gas evolution from the mixture of fuel and oxidizer. In some instances an appreciable lag occurs, as much as 5 minutes, between the initial contacting of the fuel and the oxidizer before appreciable gas evolution begins; thus the mixture may stand for as long as 5 minutes. The more reactive fuels produce a definite effervescence.

Reactive organic compounds which contain chemically bound halogen ions are not appreciably benefited by the presence of the inorganic halide promoters of this invention and are not a part of this invention.

The reactive non-halogenated liquid organic fuels embrace many classes of organic compounds but do not necessarily include all the members of any one class. Examples of classes containing reactive species are:

(l) Unsaturated hydrocarbons: olefinic, such as pentenes, octenes; acetylenic, such as butynes; diolefinic, such as cyclopentadiene; polymers such as propylene tetramer. Aromatic hydrocarbons containing an unsaturated sidechain. Reactive mixtures of unsaturated hydrocarbons and saturated hydrocarbons such as turpentine.

(2) Compounds consisting of carbon, hydrogen and sulfur: mercaptans, such as butyl mercaptan, benzyl mercaptan; sulfides such as ethyl sulfide, butyl sulfide; disulfides such as dimethyl disulfide, dibutyl disulfide; tri and higher polysulfides.

(3) Compounds containing carbon, hydrogen and nitrogen, such as aliphatic amines and aromatic amines.

(4) Organic phosphines and borines, particularly the aliphatic phosphines and borines containing not more than about 24 carbon atoms.

(5) Organic thiophosphites and thioborates. The aliphatic-thiophosphites and thioborates are preferred. The very reactive tri-aliphatictrithiophosphites contain not more than 12 carbon atoms.

(6) Organic amido compounds of phosphorus, boron and sulfur. Examples are tri-diethyltriamidophosphite; di dimethyldiamidomethylthiophosphite; dipropylamidodiethylthioborate; tri-dimethyltriamidoborate.

(7) Many oxygenated compounds are reactive, particularly those containing in addition to oxygen, nitrogen, sulfur, phosphorus and boron.

(8) Mixtures of the more reactive compounds and inactive compounds such as parafiins, benzene, petroleum distillates, alcohols and inactive members of the above generic classes.

It is to be understood that the above classes and examples do not include all the reactive fuels and that this invention is not limited to the specific classes and examples listed above.

For some uses the more reactive fuels do not require a promoter. However, for lower temperature operation, e.g., below 0 F., even these fuels are benefited by the presence of a halide promoter. The presence of a halide promoter is particularly beneficial when it is desired to operate with an oxidizer containing am. monium nitrate. The presence of ammonium nitrate appears to have a catalytic effect on the activity of the mixed fuel and results in much shorter ignition delays at the same temperature than when using aqueous hydrogen peroxide alone. The amount of halide promoter needed will be dependent on the degree of reactivity needed. In general the amount of halide promoter used will be below about 25 volume percent based on the mixed fuel. However, usually the amount of promoter used will be between about 0.1 and 10 volume percent.

The ignition characteristics of various fuels were studied using a drop test. This method utilizes a test tube, 1 in. x 4 in., containing about 0.5 ml. of oxidizer. The fuel to be tested was drawn into a hypodermic syr nge. It was then ejected forcibly against the oxidizer surface by depressing'the syringe plunger By this method amounts of fuel of'as little as 0.01 ml. can be added. Low temperature tests were carried out by cooling the test tube and the oxidizer contained therein by means or a bath; a drying tube inserted into the top of the .test tube excluded moisture. The fuel was cooled separately to the desired test temperature. By supercooling it was possible to carry out tests at temperatures below the freezing point of the fuel and/or the oxidizer.

The ignition delay, which is the time el-apsing between the addition of fuel to'the oxidizer and ignition thereof, was determined visually as either (a') very short, which corresponds to substantially instantaneous ignition, (b) short, which corresponds to substantially less than 1 second, and (c) more than 1 second, which time was determined by a stop watch.

The following tests illustrate the activity of some of the halide promoters and mixed fuels of this invention X Slight reaction evidenced bygas evolution. v Vigorous efiervescence after 10 seconds. I Immediate vigorous eifervescence.

Test D The effect of the presence of halide promoter in an alkyl sulfide (thioether), ethyl sulfide, was tested at +70 F. using 0.5 ml. of 90% H O 40% NH NO oxidizer.

with hydrogen peroxide oxidizers.

- V Mixed fuel Test A 1011 In this 'test, several halide promoters were examined R1111 Promoter ix- Added 23233 for reactivity with 0.5 ml. of hydrogen peroxide oxidizers; t 1 .each run was carried out at +70 F. Percent Promoter Oxidizer Ignition Run No. Promoter added, Hzordelay, 13.018 92 8 i New, as: as .2 as 2.; P sion 95 s 0120 22 2 as a z r s 8: g 14 SiCla so 10 0.10 0. 03 so so Short 0. 02 to o 0. 0 80 0 e Slight reaction evidenced by gas evolution. 0. 05 80-2 h r f Immediate vigorous etiervescence. 0- 10 0 .2 Vigorous efiervescence after 5-15 seconds. 0.10 9040 35 0.06 90- 0 Test E 0.06 90-40 V 8-38 8 (0 V The efiect of the presence of hahde promoter in a 1 0 s dia'lkyl disulfide was tested at +70" F. using 90% hydro- (L10 9040 32 gen peroxide as the oxidizer.

Noignition-efferveseence. 40 V H v No ignition-vigorous efi'ervescence. Mixed fuel No ignition-moderate eflervescence. Ignition Test B Run No. Fuel Promoter Fuel, Prodelay,

vol. moter, Added, seconds The effect of the presence of hahde promoters 1n a percent g m dripolene fraction fuel was tested at +70 F. using 0.5 ml. of hydrogen peroxide oxidizer. The dripolene 100 0.07 127 fraction was obtained by vacuum dlstlllation of the hqurd 9s 2 0.06 3 'by-p'ro'duct of the high temperature cracking of ethane g? g 3%: g and propane. The fraction used had an ASTM distilla- 100 0: 07 tion-JBP, 230 F; 320 F.; 90%, 388 F.; and 95 5 M8 42 Max, 424" Bromine number, 113: Maleic anhydride value, 21: Freezing point, -70 F. This fuel contained aromatics, olefins, diolefins and saturates.

1 Slight reaction evidenced by gas evolution. 4 Noignition-some eflervescence.

3 Flash followed by vigorous efiervescence.

4 Moderate eflervescence after 4 minutes.

Test C The effect of a halide promoter in a pure olefin, '2- methylebutene-l, was tested at +70 F. using 0.5 m1. of oxidizer. g

I-DimethYl disulfide. II-Diethyl disulfide. h N o ignition-some eflervescence.

Test F The effect of the presence of halide promoter in trialkyl trithiophosphite was tested at F. using 0.5 ml. of hydrogen peroxide oxidizer.

1 Triethyl trithiophosphite.

2 Tri-n butyl trithiophosphite.

3 50% trimethyl trithiophosphite50% benzene. i N o ignitionefiervescence.

No ignition-vigorous efier-vescenoe.

7 Test G In order to more precisely note the effect of the presence of halide promoter in trimethyl trithiophosphite, runs were made at lower temperatures with various hydrogen peroxide oxidizers.

w No ignition-eiiervescence.

Test H The effect of the presence of a halide promoter in alkylphosphine was tested at. -30? F; using 0.5 ml. of

80% H as the oxidizer.

Mixed fuel Pro- ' Run No. Fuel meter Fuel, Pro- Ignition v01. meter, Added, delay,

percent vol. m1. seconds percent S P013 98 2 0. 06 Short- Mono(n-octyDphosphine.

It is apparent from the data presented above that this invention can be used to generate gas at high pressure. This gas can be usedfor operating machinery such as compressed air hammers or for aircraft catapults; an

other important use for this high pressure gas is in the starting of the turbines of jet-type engines. The invention is particularly useful for operations which require a compact power plant that is able to produce a large amount of energy over a very short period of time.

Other examples of uses of this invention are: the rocketassisted takeoff or flight of aircraft; aerial missiles; boosters for surface vehicles.

The relative proportion of oxidizer-to-fuel used will depend upon the type of operation, the temperature of operation and the type of fuel and oxidizer being used. When using a 80% H O 30% NH NO solution as the oxidizer and a trimethyl trithiophosphite-PCl blend as the fuel, between about 4 and 5 volumes of oxidizer are needed per volume of fuel.

By way of example this invention is applied to the propulsion of a surface-to-air missile. The annexed figure which forms a part of this specification shows schematically the bipropellant feed system and the motor of this missile. This missile is suitable for operations wherein the fuel and the oxidizer can be maintained at a temperature high enough to insure at least a short ignition delay, e.g., when using the above oxidizer and fuel combination, a temperature of about -ZO F.

In the drawing vessel 11 contains a quantity of gas at high pressure; this gas must be inert with respect to the oxidizer and the fuel; suitable gases are nitrogen and helium. Herein helium is used as the inert gas. Helium from vessel 11 is passed through line 12 and through valve 13 which regulates the flow of gas to maintain a constant pressure beyond valve 13. From valve 13 helium is passed through lines 14 and 16 into vessel 17 and simultaneously through line 18 into vessel 19.

Vessel 17 contains the oxidizer.

Helium pressure forces the oxidizer out'of vessel 17 through line 21 to valve 22. Valve 22 is a solenoid actuated throttling valve. Suitable electrical lines connect valve 22 to an electrical source and operating switch (not shown) at the control chamber at the launching site. The oxidizer is passed through line 23. and injector 24 into combustion chamber 26. Combustion chamber. 26 is provided with an outlet nozzle 27.

Vessel 19 containsthe fuel. Vessels 17 and 19 are constructed to withstand the high pressure imposed by the helium gas. The gas pressure forces fuel from vessel 19 through line 28 to solenoid actuated throttling valve 29. Valve 29 is similar in construction and in actuation to valve 22. The fuel is passed through line 31 and injector 32 into combustion chamber 26.

Valves 22 and 29 are of such a size and setting that a predetermined ratio of oxidizer-to-fuel is passed into combustion chamber 26. Injectors 24- and 32 are so arranged that the streams of oxidizer and fuel converge and contact each other forcibly, resulting in a very thor- -80%30% solution per volume of mixed fuel (97% tr-imethyl trithiophosphite-3% PCI is introduced into the combustion chamber.

almostinstantaneouslyupon contact in the combustion the missile toward its target.

Thus having described the invention, what is claimed is:

l. A method of generating gas, which method comprises injecting separately and essentially simultaneously intothe combustion chamber of a gas generator (1) a hypergolic mixed fuel consisting essentially of (1') between about 0.1 and 10 volumepercent, based on mixed-fuel,

of a halide promoter selected from the class consisting 0f BX3, PX3, 5X2, S X and TiX4, wherein X is 5%- lected from the class consisting of chlorine and bromine and (ii) a liquid fuel selected from at least one member of the class consisting of pentene, octene, butyne, cycl0- pentadiene, propylene tetramer, turpentine, butyl mercaptan, benzyl mercaptan, ethylsulfide, butylsulfide, dimethyl disulfide, diethyl disulfide, dibutyl disulfide, tri-diethyltriamidophosphite, di-dimethyldiamidomethylthiophosphite, dipropylamidodiethylthioborate, tri dimethyltriamidoborate, trimethyl trithiophosphite, triethyl trithiophosphitc, tri-n-lbutyl trithiophosphite, and mono(n-octyl) phosphine and (2) an oxidizer selected from the class consisting of (a) aqueous hydrogen peroxide solutions consisting of at least about weight percent of H 0 and the remainder essentially water and (b) aqueous hydrogen peroxide-ammonium nitrate solutions wherein the hydrogen peroxide-Water portion is the predominant component and consists of at least about 80 weight percent of H 0 and the remainder essentially Water, in an amount and at a rate sufiicient to initiate a hypergolic reaction With and to support combustion of the fuel.

2. The method of claim 1 wherein said fuel is trimethyltrithiophosphite.

3. The method of claim 1 wherein said fuel is monooctylphosphine.

4. The method of claim 1 wherein said fuel is dimethyldisulfide.

5. The method of claim 1 wherein said fuel is Z-methylbutene-Z.

6. The method of claim 1 wherein said fuel is propylene tetramer.

7. The method of claim 1 wherein said promoter is PC13- 8. The method of claim 1 wherein said promoter is PBr 9. The method of claim 1 wherein said promoter is TiCl Theoxidizcr and the fuel react I 10. The method of claim 1 wherein said promoter is S01 11. The method of claim 1 wherein said promoter is BCl 12. The method of claim 1 wherein said oxidizer consists of about 80 weight percent of H and the remainder essentially water.

13. The method of claim 1 wherein said oxidizer consists of about 90 weight percent of H 0 and the remainder essentially water.

14. The method of claim 1 wherein said oxidizer consists of a solution of hydrogen peroxide, water and ammoni um nitrate, wherein the nitrate content is about weight percent and the hydrogen peroxide-water portion consists of about weight percent of H 0 and the remainder essentially water.

15. The method of claim 1 wherein said oxidizer consists of a solution of hydrogen peroxide, water and ammonium nitrate, wherein the nitrate content is about 40 weight percent and the hydrogen peroxide-water portion consists of about weight percent of H 0 and the re- 10 mainder essentially water.

No references cited. 

1. A METHOD OF GENERATING GAS, WHICH METHOD COMPRISES INJECTING SEPARATELY AND ESSENTIALLY SIMULTANEOUSLY INTO THE COMBUSTION CHAMBER OF A GAS GENERATOR (1) A HYPERGOLIC MIXED FUEL CONSISTING ESSENTIALLY OF (I) BETWEEN ABOUT 0.1 AND 10 VOLUME PERCENT, BASED ON MIXED FUEL, OF A HALIDE PROMOTER SELECTED FROM THE CLASS CONSISTING OF BX3, PX3, SX2, S2X2, SIX4 AND TIX4, WHEREIN X IS SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE AND (II) A LIQUID FUEL SELECTED FROM AT LEAST ONE MEMBER OF THE CLASS CONSISTING OF PENTENE, OCTENE, BUTYNE, CYCLOPENTADIENE, PROPYLENE TETRAMER, TURPENTINE, BUTYL MERCAPTAN, BENZYL MERCAPTAN, ETHYLSULFIDE, BUTYSULFIDE, DIMETHYL 